Abstract
BackgroundRotational acetabular osteotomy (RAO) is a type of pelvic osteotomy performed to improve the acetabular bony coverage against the femoral head for patients with acetabular dysplasia. The acetabular bony coverage is ideally evaluated three-dimensionally; however, there is a paucity of published data regarding three-dimensional morphology in patients with long-term excellent outcome after RAO. The present study investigated the characteristics of three-dimensional acetabular morphology with long-term excellent outcome after RAO in comparison to patients with normal hip joints and those converted to total hip arthroplasty (THA) after RAO because of osteoarthritis (OA) progression.MethodsAnteroposterior plain radiograph and computed tomography data of 57 hip joints (17 joints with excellent outcome 20 years or more after RAO, 16 normal joints, and 20 joints converted to THA after RAO) were analyzed. The two-dimensional lateral center-edge (CE) angle from plain radiographs and acetabular anteversion, anterior acetabular sector angle, and posterior sector angle from computed tomography (CT) images were calculated.ResultsCompared with patients converted to THA, all parameters in patients with long-term excellent outcome after RAO were similar to those in patients with normal hip joints, particularly in the three-dimensional analyses. The anterior bony coverage was excessive, whereas the posterior bony coverage was deficient in patients converted to THA after RAO. Anterior bony impingement and posterior instability may be the cause of OA progression after RAO.ConclusionCaution must be taken to avoid rotating the separated fragment excessively to the anterior direction during RAO to prevent OA progression and achieve long-term excellent outcome.
Highlights
Rotational acetabular osteotomy (RAO) is a type of pelvic osteotomy performed to improve the acetabular bony coverage against the femoral head for patients with acetabular dysplasia
Rotational acetabular osteotomy (RAO), which rotates the roundly separated acetabular bone to the lateral direction and improves the acetabular bony coverage against the femoral head, is a surgery to improve the biomechanical problems in patients with acetabular dysplasia [1, 2], including mechanical stress concentrated at the lateral edge of the acetabulum, instability of the hip joint, and increased stress to the labrum of the hip joint (Fig. 1)
In the total hip arthroplasty (THA) group, the morphology of the acetabulum was retroverted in the supine position, which is the body positioning during computed tomography (CT) examination, in 10 out of 20 hip joints; the retroverted acetabulum was present in only 1 hip joint in the RAO group, and it was not observed in the normal group
Summary
Rotational acetabular osteotomy (RAO) is a type of pelvic osteotomy performed to improve the acetabular bony coverage against the femoral head for patients with acetabular dysplasia. Favorable postoperative long-term outcomes have been reported in several studies [3,4,5,6,7,8]; there are some cases that require conversion to total hip arthroplasty (THA) because of the early progression of osteoarthritis (OA) after RAO [9]. These reports have focused on the two-dimensional bony coverage typified by the center-edge (CE) angle in the plain anteroposterior radiograph of the hip joint; the acetabular bony coverage should ideally be evaluated three-dimensionally [10, 11]. The aim of the present study was to demonstrate the three-dimensional acetabular morphology in patients with excellent long-term outcome after RAO in comparison with those in patients who required conversion to THA after RAO and patients with normal hip joint
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